Process of preparing cellulose derivatives



May 22, 1951 L. N. ROGERS ET AL PROCESS OF PREPARING CELLULOSEDERIVATIVES Filed Sept. 10. 1948 Sr@ Mm. view/wm @Mlm/@m MH@ d m. .M @m6[In f WB@ Patented May 22, 1951 UNITED srarss PROCESS F PREPARINGCELLULOSE DERIVATIVES Application September 10, 1948, Serial No. 48,732

, 16 Claims. l

This invention relates to an improved process for the preparation fromcellulose pulp of salts of acidic ether derivatives of cellulose, andmore particularly to a process for the preparation of salts of an acidicether derivative of cellulose of the group consisting of cellulose etherderivatives of aliphatic carboxylic and alkyl sulfonic acids having notmore than 4 carbon atoms, as for example water-soluble salts ofcarboxymethyl cellulose and of cellulose ethane sulfonic acid.

Cellulose .derivatives of the character indicated are highly useful inlaundry operations, in which they enhance the action of the detergent,apparently by retaining in suspension the dirt particles removed fromthe fabrics, whereby graying of the fabric on repeated washing with thedetergent composition is reduced. This ability of a detergentcomposition to maintain the whiteness cf white fabrics on repeatedWashing is sometimes referred to as whiteness maintenance. Furthermore,these cellulose derivatives tend to prevent the deposition on the fabricof insoluuble salts, and thus tend to reduce the harsh feel so impartedto the fabrics, especially when the detergent is of low grade. For thisand related purposes, thesolubility of the cellulose derivatives inwater is quite important to effective results, and clarity is desirable.When, as is often the case, the derivative is to be mixed with thedetergent While fluid, derivatives having low Viscosity, adapted for usein conventional mixing equipment such as crutchers and the like, arepreferable. Moreover, there has been some indication that thosecellulose derivatives, which give low-viscosity aqueous solutions, havegreater efficiency in improving `the whiteness maintenance of detergentcompositions.

It is accordingly an object of the invention to provide a novel processfor the eiiicient low-cost production of salts of acidic etherderivatives of cellulose, which salts form clear solutions in water, arehighly elective, and which have a viscosity suiciently low to facilitatehandling with convenient detergent making equipment.

It is a feature of the instant process that the cellulose derivativesmay be produced continuously; in the preferred process the cellulosepulp is conveyed through each of the treatment zones in the form of acontinuous sheet, emerging in sheet form after conversion to the ethersalt for delivery to crushing and grinding equipment. It is`particularly important to pass the material through the etherifying zonein the form cf a continuous sheet in order that the final product mayhave the desired properties, as hereinafter more fully explained.

It is a further object of the invention to provide a method cf formingcellulose derivatives of the character described which includes the stepof etherifying a sheet of cellulose bythe application to the sheet ofliquid reagents in amount which is at no time greater than the amount ofliquid which the sheet is capable of absorbing.

It is a further object of the invention to pro--` vide a process ofetherifying cellulose which includes the steps of applying thereto insuccession, and in the order named, an alkaline agent,v a halogenatedlower fatty acid, or halogenated lower alkyl sulfonic acid, and analkaline agent, in total amount not greater than that which the sheet iscapable of absorbing.

More specifically, it is an object of the invention to provide a new andimproved process for the manufacture of carboxymethyl cellulose whichinvolves feeding the pulp continuously in, sheet form in succession, andin the order named. through a hydrolyzing zone, a Washing zone, a dryingzone, an etherifying zone, a ripening Zona..

cosity, water soluble carboxymethyl cellulose. It will be understood,however, that the process isn readily applicable to the preparation ofcellulose ethers of other aliphatic carboxylic acids having,

not more than 4 carbon atoms per molecule and of lower alkyl sulphonicacids having not more than 4 carbon atoms per molecule by appropriatesubstitution of reagents, and that the use of speciiic languagedescribing the preferred embodiment of the invention is not intended tolimit SCOpe.

The following specific examples are illustrative: of preferred methodsof processing cotton linters, in sheet form to produce the acidic ethersof cel-` lulose.

Example I A lil-pound roll of cotton linters sheet, l0 inches wide and0.040 inch thick, and a viscosity of 1l seconds when 2.5 grams aredissolved in cuprammonium according to the A. C. S. Standard Method, waspassed continuously through a hydrochloric acid bath at 70 C. andcontaining 15% hydrogen chloride.

The speed was so regulated that the contact time of the paper with theacid Was 60 seconds. During this time the vis cosity was reduced to 20seconds, as measured by the A. C. S. method, using a -gram sample, butother characteristics of the paper such as strength and absorbencyremained practically unchanged. The sheet was then passed throughsqueeze rolls to remove the excess acid, and then alternately throughthree successive Water Washes and squeeze rolls to remove the remainingacid, and finally through a roll dryer and partially dried to about 20%moisture.

The dried sheet was passed through a series of saturating rolls (coatingrolls) to spread uniformly over both sides of the sheet 10 pounds of 35%aqueous sodium hydroxide. The resultant sheet, showing very littleshrinkage, Was immedi ately passed through a second set of saturatingrolls to coat onto the paper 8.9 pounds of an aqueous solution preparedby adding to 19 pounds of 80% chloracetic acid solution 1.8 pounds ofdry soda ash, and finally through a third set of saturating rolls tocoat 7 pounds of 35% sodium hydroxide.

The sheet Was then passed (a) through a nondrying oven at 190 C. for aperiod of 4 minutes of ripening, (b) through a tank containing carbondioxide gas (15 seconds), (c) over a second roll dryer to dry to 3%moisture and, (d) into crushing and grinding equipment.

The product dissolved readily in water to form a free flowing 2%solution which, when adjusted to pH 7, Was substantially water clear.

Example II The procedure was the same as Example I except that the sheetwas coated first with l2 pounds of 35% aqueous sodium hydroxide then 8pounds of 80% chloracetic acid, and nally 8 pounds of sodium hydroxide.The product was similar to that of Example I.

Example III The procedure was the same as Example I except that thehydrolysis, washing, and partial drying Were omitted. The product formeda gel when prepared into 0.5 solution.

Example IV A l-pound roll of absorbent cellulose sheet, l inches wideand 0.040 inch thick, was passed continuously through a hydrochloricacid bath at 67 C. and containing 20% hydrogen chloride. The speed wasso regulated that the contact time 0f the paper with the acid was 45seconds. During this time the viscosity was reduced to 25 seconds, asmeasured by A. C. S. method using a gram sample, but othercharacteristics of the paper such as strength and absorbency remainedpractically unchanged. l The sheet was then passed through squeeze rollsto remove the excess acid, and then alternately through three successiveWater Washes and squeeze rolls to remove the remaining acid, and Iinallythrough a roll dryer and partially dried to about 32 moisture.

The dried sheet was passed through a series of coating rolls to spreaduniformly over both sides of the sheet 7.2 pounds of 29% aqueous sodiumhydroxide. The resultant sheet, showing very little shrinkage, wasimmediately passed through a second set of saturating rolls to coat ontothe paper 7.3 pounds of a solution prepared by adding 2.0 pounds oisodium carbonate to 19 pounds of a 70% aqueous solution of mono` Circhloracetic acid, and nally through a third set of saturating rolls tocoat 8.4 pounds of 29% sodium hydroxide.

The sheet was then passed (a) through a non drying oven at 120 C. for aperiod of 3 minutes of ripening, (b) 'through a tank containing carbondioxide gas (ll seconds), (c) over a second roll dryer to dry to 3%moisture and, (d) into crushing and grinding equipment.

Over 97% of the product was soluble in Water when dissolved to make a 2%solution and adjusted to pI-I 7. This solubility was less than that ofExample I, but the product Was eminently suitable as a detergent aid.

Eample V A -pound roll of absorbent cellulose sheet, l0 inches Wide and0.622 inch thick, was passed continuousiy through a hydrochloric acidbath at 70n C. and containing hydrogen chloride. The speed was soregulated that the contact time of the paper with the acid was 90seconds. During this time the viscosity was reduced to l5 seconds asmeasured by A. C. S. method using a -gram sample, but othercharacteristics of the paperA such as strength and absorbency remainedprac tically unchanged. The sheet was then passed through squeeze rollsto remove the excess acid, and then alternately through three successiveWater Washes and squeeze rolls to remove the remaining acid, and nallythrough a roll dryer and partially dried to about 9.0% moisture.

The dried sheet was passed through a series of two or more saturating(coating) rolls to spread uniformly over both sides of the sheet l2pounds of 34% aqueous sodium hydroxide. r.The resultant sheet, showingvery little shrinkage, Was immediately passed through a second set ofsaturating rolls to coat onto the paper 12 pounds of a solution preparedby adding 1.8 pounds of sodium carbonate to l0 pounds of 80% aqueoussolution of monochloracetic acid, and nally through a third set ofsaturating rolls to coat 7.1 pounds of 34% sodium hydroxide.

The sheet was then passed (a) through a non-` drying oven at 90 C. for aperiod of 6 minutes of ripening, (b) through a tank containing carbondioxide gas (22 seconds), (c) over a second roll dryer to dry to 3%moisture, and (d) into crushing and grinding equipment.

The product was readily and completely soluble in water when dissolvedto make a 2% solution, and when adjusted to pI-I of 7 this solution waswater clear.

Example VI The procedure was the same as Example I except that the paperwas coated rst with 9.5 pounds of sodium hydroxide, then with 11.5pounds of an aqueous solution containing 75% alpha chloro propionic acidwhich was neutralized with soda ash, and nally with 8.6 pounds of 35%sodium hydroxide.

Example VII The procedure Was the same as Example VI except that theacid used in the second coating step was 10.2 pounds of chloro-ethanesulfonic acid. The product was very similar to carboxymethyl cellulose,and had excellent properties as a detergent added.

Other halogenated acids which may be employed to form acidic etherderivatives of cellulose are chlorobutyric acid, chloropropane sulfonicacid, bromobutane sulfonic acid and chlorohydroxy propane sulfonic acid.

The apparatus 'shown in the drawing may be used to carry outv thelprocesses justA described. r17h-us Athe fibrous sheetv which isdesignated throughout by the reference character I0, initiallyconstituted by absorbent cellulose sheet having the characteristics setforthv in the eX- ample, is drawn continuouslyl from a roll I2 by drawrolls I3 and passed through hydrochloric acid in tray i5, beingsupported therein yby rollers 1.6. Following depolymerization lorhydrolysis in the acid bath and consequent reduction of viscosity, thesheet is led between squeeze rolls I1 and is washed with water, toremove the acid.

Itv is then led over heated drying rolls i8, or

through any conventional roll dryer, where it is dried to the speciedmoisture content.

The partly dried sheet of depolymerized cellulose vis then passedthrough a series of two-or more sets of saturating or coacting rolls,two sets being shown in the drawings, to apply caustic 'to the sheet.Each set of coating rolls may comprise three superposed rolls J, thesheetV being fedbetween the several rolls so as to absorb the causticwhich is fed onto the rolls from-troughs on side of rolls similar tothose used in the paper industry for saturating paper. It will be notedthat the sheet is not submerged in the solution. By suitable selectionof the number of sets ofrolls and their diameters, the amount of causticsupplied can be determined with exactness.

From the causticl rolls the sheet is fed directly to coating rolls 25,of which several sets are similarly provided, whereby the halogenatedacid is supplied to the sheet from troughs, on side of rolls same asabove. From these rolls thesheet is passed directly to one or more setsof rolls 28, functioning similarly to 'the coating rolls hereinbeforedescribed, by which the final application of caustic from troughs areeffected.

The sheet is then fedvinto a ripening cabinet 3U in which it issupported on a series o'superposed continuous conveyors 3l, alternateconveyors being driven in opposite directions, whereby the sheet ispassed along each conveyor :from the uppermost to the lowest of theseries. Cabinet is heated from steam coils 32 in bottom of cabinet. Highhumidity is maintained.

Upon leaving the ripening cabinet, the sheet is fed into a neutralizingchamber which isr supplied with carbon dioxide gas, the sheet beingsupported on rolls 36. from a chamber38 in which chloracetic acid to besupplied rolls 25 is partially neutralized with sodium carbonate, asdescribed more fully hereinafter.

The Vsheet is then passed between screen conveyors L30, 4i which areentrained over'drying rolls 43, and is then fed by positively drivenrolls to a conventional grinding or pulverizing mill The type of pulpused may vary widely, the processing conditions beingv altered to treateffectively the selected' pulp. Cotton linters is the preferredmaterial, but wood, straw, bagasseor other cellulosic material may beemployed. The viscosity of the initialr pulp obviouslyaffects materiallythe selection or processing condi-tions for the production of aderivative having specified characteristics.

The strength of the pulp sheet should, o1" course, be sufcient to ensureagainst breakage as the sheet is passed through the various treatmentzones, but the mullen (tear) value should below, for ready penetration.Values of Vthe order of 25 The gas may be derived 48, thev groundmaterial being delivered to Va 'hinV to "40 mullen, measured on a sheet0.040'in`ch" thick, aresatisf'actory, lthis being the'optimum thicknessof sheet'. However, the sheet thickness may vary substantially, cottonlinters sheets ofi As has been pointed out, processing conditions. maybe varied rather widely depending upon the' initial pulp and the natureof the nal product.`

The following more vdetailed discussion of the several steps of theprocess are indicative of the variations in processing conditions whichare possible.

Acid hydro-lysis The hydrolysis or ldepolyn'ierization of the 'cellulosemay be effected with a wide variety of' acids, inorganic mineral acidssuch asy hydrochloric, sulfuric, nitric, and 'phosphoric 'being commonlyused. Hydrcchloric acid is preferred,

and the limits and conditions specified herein relate to this acid.

In order to produce carboxymethyl cellulose having a viscosity vin a 2%aqueous solution (pH '7) of less than 100 centipoises, for example. 2.5,to centipoises, the hydrolyzed sheet should' have a' viscosity of' 12 to36 seconds, when measured by the standard method of the AmericanChemical Society, using a 5gram sample. When pulp such as described inthe foregoing specicexample, having a viscosity of 11 seconds (Z5-gramsample) is employed, the concentration of hydrochloric acidshould befrom about 5% to aboutV 30% by weight, preferably betweenV 13% and 17%.If the acid concentration is 15%, the time of contact between acid andpulp may vary from 30 to 90 seconds. If the acid concentration is heldat 15% and the contact,Y time to seconds', the temperature of the bathmay vary between 60 and 80 C. It is the primary purpose in conductingthis stepto hydrolyze the ber without reducing the liber strengthmaterially and without substantial swelling of the sheet, andtemperatures from about 50 C. to about 100 C. and time from aboutr l5 toabout 200 seconds andother'processing conditions are selected with thisend in View. Excellent results are achieved, using the pulp of ExampleI, by the use ofY 15% hydrochloric acid at a temperature of to 80 C.,the sheet being immersed for a period of 60 seconds. `v

` Washing and. drying Itis an important feature of the invention thatetheri'c'ation of the cellulose is effected by absorption of thereagents in the brous sheet, no

excess of reagent being applied at any time. It isth'erefore necessaryto remove the hydrolyzing acid and at least partially dry the sheet'Vprior tok weight of the sheet when dry.

Etherifcatz'on A significant feature of. the instant invention is theapplication of the alkaline agent, for in- Preferably drying iscontinued until the moisture of the sheet is .from 10% to V25% by'stance caustic soda, in two steps which respectively precede and followthe application of the esterifying agent, such as chloracetic acid,bromacetic acid or other halogenated aliphatic carboxylic acid or alkylsulfonic acid having not more than 4 carbon atoms, chloracetic acidbeing most generally applicable, however, The chief effects of thedouble causticization are to ensure more uniform penetration, lessswelling of the pulp, and less heating and therefore less decompositionof the chloracetic acid, for example, and to eifect correspondingimprovements in solubility and clarity of the product. The causticserves to further the reaction between chloracetic acid and cellulose,either by combining with the halogen of the chloracetate and causing theresultant free radical to combine with the hydroxyl of the cellulose, orby combining with the hydrogen chloride formed in the reaction.Mercerization (i. e. conversion of all of the cellulose to alkalicellulose) is undesirable in the instant process, and is eiectivelyavoided by the absorption of ail of the caustic in the cellulose sheet,there being no unabsorbed solution in contact with the cellulose at anytime. For instance, the contraction of the sheet (a measure of theamount of swelling) when processed by the present invention is less than3%, Whereas a similar sheet dipped in caustic of the same strengthcontracts from 15 to 20%. `Since swelling tends to close the intersticesof the sheet, the initial application of caustic as proposed hereinresults in a sheet which is quite porous and absorptive, and whichtherefore can absorb and distribute uniformly a relatively viscoussolution of halogenated acid of high concentration. It is thereforedesirable to limit the amount of caustic initially applied so as toeliminate swelling before application of halogenated acid, and to addthereafter an additional amount of caustic. In the case of the use ofcaustic soda and ohloracetic acid this additional amount is preferablysuincient to bring the total weight of NaOH to substantially the weightof actual chloracetic acid introduced.

While any alkaline agent of adequate strength may be employed, alkalimetal hydroxides function most satisfactorily, and caustic soda ispreferred.A When using caustic soda, the concentration may vary from 25%to 40% and the temperature from 15 to 40 C. In the initialcausticization step, We prefer to add slightly over half of the totalamount of caustic required, for instance 60%, or about 1.2 to about 2.2mols per glucose unit, the balance of about 1.0 to about 1.4 mols beingadded in the second causticizing step. By applying the caustic on aplurality of sets of rolls, more uniform distribution is obtained andthe product correspondingly improved. A higher concentration of causticcan be used if the temperature of the solution is raised sumciently toavoid viscosity difficulties; a concentration of less than 25% should beavoided, however, because introduction of too much water retardssubsequent reaction by formation of a gel, mercerization or swelling.

The acid preferably used in the preparation of carboxymethyl celluloseis an aqueous solution of monochlcracetic acid (ClCmCOOH), the acidconcentration ranging from 60% to 80% and the temperature from 15 to 40C. An 80% solution of chloraceticacid corresponds to the solubility ofthe acid at room temperature, and at higher temperatures the acid tendsto hydrolyzed. Lower concentrations than 60% introduce sufficient waterto result in gellation of the product and'reduce the workability` of thesheet. The amount of actual chloracetic acid used may vary between about50% and 100% by Weight of the pulp being treated. Preferably we employfrom about 0.8 to about 1.5 mols of acid per glucose unit or from about0.45 lb. to about 0.88 lb. of actual chloracetio acid per pound ofhydrolyzed cellulose, the ratio selected depending upon the degree ofsubstitution and the clarity of the product desired.

The acid may be partially neutralized with an alkaline agent, beforeapplication to the sheet to decrease the heat of neutralizationliberated in the sheet and to reduce corrosion of equipment. Ashereinbefore indicated, the employment of sodium carbonate for thispurpose is helpful since the carbon dioxide gas which is liberated maybe used in the nal neutralization step, as indicated hereinbefore.

Complete neutralization of the chloracetic acid at this pointisundesirable, and there are a number of factors to consider indetermining4 the most desirable extent of neutralization. Thus whenlarge quantities of salt are formed, much of the salt fails to go intosolution, the viscosity of the solution is increased, and there is agreater tendency toward foaming. On the other hand, as the extent ofneutralization is decreased, the aforementioned advantages of neu-Ytralizing are realized in less degree. We prefer to neutralize from 30%to 50% of the chloracetic acid, neutralization of about 40% givingoptimum results.

In order to produce carboxymethyl cellulose which is readily soluble inwater, the final product should contain as an average at least 0.4 andpreferably 0.6 to 1.0 glycolic acid groups per glucose unit, and thereagents and conditions should be selected accordingly.

Following -halogenated acid impregnation, caustic is again applied tothe sheet in amounts sufficient to make up the total required. It shouldbe noted, however, that when the halogenated acid has been partiallyneutralized before application to the cellulose, the amountof causticrequired for each application may be reduced proportionately. At no timeis there excess caustic in the sheet to allow conditions of steepingrequired for the formation of alkali cellulose.

It is important to the effective practice of this step of etheriiicationthat the total amount of reagents supplied to the sheet is always lessthan that which the sheet is capable of absorbing.`

Consequently the final caustic application results in prompt absorptionand uniform distribution of reagent.

The reagents used in the etheriiication step may be applied in immediatesequence, and the time required for the material to pass through theentire set of coating rolls is usually only about one minute, rapidapplication of caustic and acid being essential to prevent swelling andother difculties.

In describing the application of the reagents as a coating step, it willbe appreciated that the term coating is not intended in a limited sense;the cellulose is promptly impregnated with the reagent by absorption,for the reason stated above.

Ripening It is a feature of the invention that the etherication reactionis completed in a non-drying `the gas.

crushing occurs in the dryer.

or humid atmosphere, and to this end the impregnated sheet may beconveyed through a ripening cabinet which may be humidiiied by theintroduction of steam. This is desirable in order to eliminate anysubstantial drying with resultant lack of control of the degree ofsubstitution. A relative humidity or" 90 is found to be entirelyadequate for the purpose.

The conveyors in the ripening chamber are de signed to retain the sheetin the chamber for a period of time which varies with the temperau tureselected. If a temperature of 100 C. is established in the chamber, aperiod of 4 minutes is satisfactory, and the ripening time may bedecreased to 3 minutes at a temperature of '120 C. As the temperature islowered, the time in creases rapidly, l minutes being required at 80 C.The time and temperature may vary considerably, periods of ripening offrom one to 20 minutes Aand temperatures of from 60 to 130 C.

being satisfactorily employed. Only very slightv color in the product ondrying, it is desirable to neutralize the etheriiied product. Carbondioxide gas, preferably derived from partial neutralization of thehalogenated acid, with sodium carbonate or other alkali metal carbonatefor example, may be employed, or Dry Ice may be introduced in theneutralizing chamber to supply Hydrogen chloride gas, aqueous hydrogenchloride, or other acidic gas such as sulphur dioxide may also be used.The gas penetrates the sheet rapidly and only a loop dip is required.This step may, of course, be omitted, where neutrality is not desired,and color control is not needed, or where the product is not to bedried.

Drying- Any type of dryer, such as an ordinary open or closed roll dryermay be employed to dry the neutralized sheet. The dry product isflexible when hot, and `brittle when cold, so that no However, the sheetis easily crushed in any conventional grinder to the desired particlesize.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

l. In the process of preparing salts of acidic ether derivatives ofcellulose from cellulose pulp, the steps which comprise (l) contactingthe pulp in the form of a continuous sheet, while feeding the vsheetthrough a hydrolyzing zone, With a mineral acid at elevated temperaturefor a period of time sufficient to effect substantial depolymerizationof the pulp, (2) Washing and drying the sheet while feeding the sheetthrough an acid removal zone, and (3) impregnating the sheet, whilefeeding the sheet through an etherifying zone, with an aqueous solutionof a halogenated acid of the group consisting of halogenated alim phaticcarboxylic and halogenated alkyl sulfonic acids having not more than 4carbon atoms in the molecule and an alkaline agent in total amount notgreater than that which the sheet is capable of absorbing.

2. In the process of preparing salts of cellulose ether carboxylic acidsfrom cellulose pulp, the steps which comprise (l) contacting the pulp inthe form of a continuous sheet, while feeding the sheet through ahydrolyzing zone, with amineral acid at elevated temperature for aperiod of time suflici'ent to effect substantia1 depolymerization of thepulp, (2) washing and drying the sheetlcellulose, the steps whichcomprise (l) `contacting Acellulose pulp in the form of a continuoussheet, whilevfeeding the sheet through a hydro- 'lyzing zone, witha-mineral'acid atelevated temperature for a period ofA time sufficientto effect substantial depolymerization of` the pulp, (2,)

'washing and drying the sheet while feeding the sheety through 'an acidremoval zone, and (3) impregnating the sheet, while feeding the sheetthrough an etherifying zone, with caustic soda and an `aqueous solutionof chloracetic acid, the amounts by weight of actualv chloracetic acidand caustic being substantially equal, and Ythe molar ratio ofVchloracetic acid to glucose unit being in the range of about 0.8:1 toabout 1.75,:1.

4. In the process of preparing a wateresoluble carboxymethyl cellulose,having a viscosity of less than c p. in a 2%aqueous solution of pI-I 7,the steps which comprise (l) contacting cellulose -pulp in a continuoussheet of thickness 00125-006 inch, Awhile feeding the sheet `through ahydrolyzing zone, with an` aqueous solution of hydrochloric acid ofconcentration of 5-30% by weight; maintaining within the zoneV avtempera,-

seconds, (2)V alternately washingand pressingjthe sheets, adding aftereach pressing an amount-of water equal in weight to the weight of thepulp while feeding through a washing zone, (3) drying at elevatedtemperatures until the moisture content of the pulp is from lil-25% byweight while feeding through a drying zone, (4) impregnating the sheetwhile feeding through an etherifying zone, first with an aqueoussolution of caustic soda of concentration 254-,40% by weight in quan.tity of about 1.2 to about 2.2 mols of caustic alkali per glucose unit,then with an aqueous solution of chloracetic acid of concentration of60-80% by weight in quantity of 0.8 to 1.5 mols of acid per glucoseunit, and finally with an aqueous solution of caustic soda ofconcentration of 2540% by weight in quantity sufficient to yield withthe caustic soda added previously an amount of sodium hydroxide equal inweight to the weight of ClCHzCOOH employed in the etherication, andmaintaining throughoutthe etheriflcation process a temperature of 15 to40 C.

5. In a process for the manufacture of salts of cellulose ethercarboxylic acids, the steps which comprise continuously feeding acellulose sheet while applying to the sheet, in succession and intheorder named, an alkaline agent, a halo-k` genated lower fatty acidhaving not more than 4 carbon atoms, and an alkaline agent, in totalamount not greater than that which the sheet is 11 being supplied insubstantially equal quantity by Weight and the acid being in the molarproportion of about 0.8 `to about 1.5 mols acid per glucose unit.

'7. In a process for the manufacture of carboxymethyl cellulose, thesteps which comprise continuously feeding a cellulose sheet whileapplying to the sheet, in succession and in the order named, aqueoussolutions of caustic soda, chloracetic acid, and caustic soda, the acidand caustic being supplied in substantially equal quantity by weight andthe acid being in the molar proportion of about 0.8 to about 1.5 molsacid per glucose unit, approximately 60% of the total caustic beingsupplied in the initial application.

8. In a process for the manufacture of carboxymethyl cellulose having adegree of substitution of 0.4-1.0 glycolic acid groups per glucose unit,the steps which comprise feeding a cellulose sheet While applying to thesheet in succession and in the order named, an aqueous solution ofcaustic soda of concentration of -40% by weight in quantity of about 1.2to about 2.2 mols of caustic per glucose unit, an aqueous solution ofchloracetic acid of concentration of E-80% by weight in quantity ofabout 0.8-1.5 mols of acid per glucose unit, and caustic soda ofconcentration of 25-40% by weight in quantity of about 1.0-1.4 mols ofcaustic per glucose unit.

9. In a process for the manufacture of salts of cellulose ethercarboxylic acids, the steps which comprise continuously feeding acellulose sheet through an etherifying zone and a ripening zone,impregnating the sheet While in said etherifying zone with aqueoussolutions of a halogenated lower fatty acid and an alkali metalhydroxide, and maintaining in said ripening zone a temperature of fromabout 60 C. to about 130 C. and a humid atmosphere, the rate of feed insaid ripening zone being such that the period of ripening is from aboutone to about 20 minutes.

10. In aprocess for the manufacture of salts of cellulose ethercarboxylic acids, the steps which comprise continuously feeding throughan etherifying zone a cellulose sheet while applying to the sheet,irl-succession and in the order named, aqueous solutions of an alkalineagent, a halogenated lower fatty acid, having not more than e carbonatoms, and an alkaline agent, in total amount not greater than thatwhich the sheet is capable of absorbing, and thereafter feeding thesheet through a ripening zone While maintaining in said zone atemperature of from about 60" C. to about 130 C. and a humid atmosphere,the rate of feed in said zone being such that the ripening is completedin from about one to about 2G minutes.

1l. In a process for the manufacture of salts of cellulose ethercarboxylic acids, the steps which comprise continuously feeding acellulose sheet through an etherifying zone and a ripening zone,impregnating the sheet While in said etherifying zone with aqueoussolutions of a halogenated lower fatty acid having not more than 4carbon atoms and an alkali metal hydroxide, and maintaining in saidripening zone a temperature of from about 60 C. to about 130 C. and ahumid atmosphere, the rate of feed in said ripening zone being such thatthe period of ripening is from one to about 20 minutes.

12. In a process for the manufacture of carboxymethyl cellulose, thesteps which comprise continuously feeding a cellulose sheet through anetherifying zone and a ripening zone, impregnating the sheet While insaid etherifying zone with a partially neutralized aqueous solution ofchloracetic acid and an aqueous solution of an alkali metal hydroxide,and maintaining in said ripening zone a temperature of from about C. toabout 130 C. and a humid atmosphere, the rate of feed in said ripeningzone being such that the period of ripening is from about one to about20 minutes.

13. In a process for the manufacture of carboxymethyl cellulose, thesteps which comprise continuously feeding a cellulose sheet insuccession through an etherifying zone and a neutralizing zone, reactingchloracetic acid with an alkali metal carbonate to effect partialneutralization of the acid with liberation of carbon dioxide gas,contacting the sheet while in said etherifying zone with the partiallyneutralized acid and an aqueous alkali metal hydroxide, and passing theliberated gas into said neutralizing zone to effect neutralization ofunreacted hydroxide in the cellulose.

14. In a process for the manufacture of carboxymethyl cellulose, thesteps which comprise continuously feeding a cellulose sheet insuccession through an etherifying zone and a neutralizing zone, reactingchloracetic acid with an alkali metal carbonate to eiect neutralizationof about 40% of the acid with liberation of carbon dioxide gas, andcontacting the sheet while in said etherifying zone with the partiallyneutralized acid and an aqueous alkali metal hydroxide.

15. In a process for the manufacture of carboxymethyl cellulose fromcellulose pulp, the steps which comprise continuously feeding cellulosepulp in the form of a continuous sheet through a hydrolyzing zone, anacid acid removing zone, an etherifying zone, a ripening zone, and aneutralizing zone, contacting said sheet While in said hydrolyzing zonewith a strong mineral acid to partially degrade the cellulose, Washingthe sheet with an aqueous liquid and heating the Washed sheet to effectremoval of washing liquid, applying to the sheet in said etherifyingzone aqueous solutions of a halogenated lower fattyacid having not morethan 4 carbon atoms and an alkaline agent and maintaining an elevatedtemperature in said etherifying zone to effect substitution of glycoiicacid groups on the cellulose chain, and contacting the sheet in saidneutralizing zone with a neutralizing agent for the unreacted remainderof the alkaline agent.

16. In a process of preparing Water soluble salts of cellulose etheralkyl sulfonic acids Where the alkyl radical contains no more than 4carbon atoms the steps which comprise continuously feeding the cellulosein the form of a continuous sheet, through a hydrolyzing zone, an acidremoval zone, a drying zone, and then impregnating the sheet whilefeeding through an etherifying zone successively and in the order named(l) with an aqueous solution of caustic alkali of concentration of:Z5-40% by weight in quantity of about 1.2 to 2.2 mols sodium hydroxideper glucose unit of cellulose, (2) with an aqueous solution of ahalogenated alkane sulfonic acid having not more than 4 carbon atoms inconcentration of about 60% to about 80% by Weight in quantity of about0.8 to 1.5 mols of acid per mol of glucose unit, (3) with an aqueoussolution of caustic alkali of concentration of 25-40% by weight inquantity of 1.0 to 1.4 mols sodium hydroxide per mol glucose unit,maintaining throughout the etherifying zone a temperature of 15 to 40C., then continuing the process while feeding the sheet continuouslythrough a ripening zone, a

fle of this patent:

14 UNITED STATES PATENTS Name Date Seel Aug. 5, 1924 Reid June 28, 1932Ellsworth Nov. 10, 1936 Maxwell Dec. 7, 1937 Freeman et al May 23, 1939Collings et a1 Apr. 7, 1942

1. IN THE PROCESS OF PREPARING SALTS OF ACIDIC ETHER DERIVATIVES OFCELLULOSE FROM CELLULOSE PULP, THE STEPS WHICH COMPRISE (1) CONTACTINGTHE PULP IN THE FORM OF A CONTINUOUS SHEET, WHILE FEEDING THE SHEET,THROUGH A HYDROLYZING ZONE, WITH A MINERAL ACID AT ELEVATED TEMPERATUREFOR A PERIOD OF TIME SUFFICIENT TO EFFECT SUBSTANTIAL DEPOLYMERIZATIONOF THE PULP, (2) WASHING AND DRYING THE SHEET WHILE FEEDING THE SHEETTHROUGH AN ACID REMOVAL ZONE, AND (3) IMPREGNATING THE SHEET, ZONE, WITHAN AQUEOUS SOLUTION OF A HALOGENATED WHILE FEEDING THE SHEET THROUGH ANETHERIFYING ACID OF THE GROUP CONSISTING OF HALOGENATED ALIPHATICCARBOXYLIC AND HALOGENATED ALKYL SULFONIC ACIDS HAVING NOT MORE THAN 4CARBON ATOMS IN THE MOLECULE AND AN ALKALINE AGENT IN TOTAL AMOUNT NOTGREATER THAN THAT WHICH THE SHEET IS CAPABLE OF ABSORBING.